EX 8200 (VC) - RE change fails

I will change the Backup RE (SRE1) in my ex8200 vs. an RE from a other ex8200 without an config but the same Junos Version.

The RE runs in the ex 8200 chassis but when i logged in the console, i see that the RE is Master. It cant be, because the SRE0 is Master in the chassis. When i logged in the SRE0 i see thet it is Master too und wenn i make show chassis Routingengine is the that SRE0 ist Master and SRE12 is Backup.

So when i make the SRE1 Master, all routed und switched pings stop. I think the SRE1 don´t has the running config.

The ex 8200 runs with an second ex 8200 and two XREs in Virtual-Chassis mode and alle connections are running between the XRE´s and RE on the ex 8200.

So what is the procedure when i will change the RE in an ex 8200?? I think it must be Plug & Play?!